The study investigated the effect of increasing dietary inclusion of Mannan oligosaccharide (MOS) on growth and blood parameters of sea bream (Sparus aurata). Varying concentrations of MOS were added to commercial sea bream feed at 0% (control), 1, 2, 3 and 4%. At the end of the 15 week trial, control group had the highest final weight, specific growth rate, feed conversion ratio and protein efficiency ratio (P<0.05), although these did not differ among the MOS containing groups (P>0.05). Survival rates were higher in the MOS treatment groups. Blood parameters, did not differ among treatment groups (P>0.05). The lowest Alkaline phosphatase (ALP) value was measured in the control group wheras the highest was recorded in the 4% MOS group. The lowest level of triglycerides was measured in the 4% MOS group, while the highest level of triglycerides was measured in the control group. Cholesterol level was lowest in the 2% MOS group (P<0.05). The study showed that the inclusion of dietary MOS has no negative effects on growth and blood parameters in sea breams. However, dietary MOS inclusion led to higher survival rate in trial fish.